Field-magnet pole piece for dynamo-electric machines



March 4, 1924. 1,485,393

D. HALL FIELD MAGNET POLE PIECE FOR DYNAMO ELECTRIC MACHINES Filed Feb. 4, 1918 7 I NET C .9 NON M06NE7 C k z 7 A Pg 2 IV F/QU C urren f WITNESSES 2 INVENTOR WM Ody/a Ha Patented Mar. 4, 1924.

UNITED STA ES PATENT orncs.

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A CORPORATION 01 .PENNSYLVANIA.

FIELD-MAGNET POLE PIECE FOB DYNAMIC-ELECTRIC MACHINES. I

Application filed February 4, 1918. Serial No. 215,373.

To all whom it may concern:

Be it known that I, DAVID HALL, a citizen of the United States, and a resident of Wilkinsbur in the count of Allegheny and 6 State Pennsylvania, ave invented a new and useful Improvement in Field-Magnet Pole Pieces for Dynamo-Electric Machines, of which the following is a specification.

My invention relates to dynamo-electric machines and it has special relation to the structure of field magnet pole pieces em ployed therein.

The object of my invention is to provide ance with my invention is provided with non-magnetic portions intersecting the flux a0 path, the length and cross-section of the non-magnetic material both being adjustable.

Referring to the drawing, Fig. 1 is a transverse sectional view of a ortion of a dynamo-electric machine embo ying my invention; Fig. 2 is a diagram showing the flux values, for various values of field current, of a pole piece embodying my invention, as compared with corresponding values for a solid pole piece.

Referring more particularly to Fig. 1, I have shown a field frame 1to which a pole iece 2 constructed in accordance with my inventior', is attached by means of a bolt 3. 5 The pole piece 2 is spaced from the field frame 1 b two interposed spacing-members 4 and 5 0 metal each of which is composed of an outside rim 6 of magnetizable material, preferably iron, and a center portion 7 of some non-magnetizable material, such, for example, as brass. Thus 'aths are provided for the ma etic lines of orce from the field frame 1, t rough the magnetizable rims 6 of the spacing members 4 and 5, to the pole piece 2. Slots 8 and 9 are cut into the pole piece at the 'unctions of the iron and brass portions of t e spacing members'4 and 5 to form fingers 10 and 11 which are parts of the magnetic circuit.

When the current in the field-magnet coil (not shown) is small, substantiallythe entire field flux is through the iron rims 4 and 5 and the-fingers 10, on account of the low reluctance of these paths, but, when the current becomes stronger, the flux passes through the brass portion of the spacing member 5 to the fingers 11. When the current is very strong, the entire pole piece is energized. Whenthe field flux is passing through the fingers 10 and the current increases, the fingers begin to approach saturation, causing the saturation curve, shown at A in Fig. 2, to bend away from a solid-polepiece saturation curve shown atB. However, the curve does not continue to bend over indefinitely because prevented by the leakage flux across the brass portion of the s acing member 5 to the fingers 11. Since ux leakage across the brass portion of the liner 5 occurs gradually, the magnetization curve A does not become horizontal but continues upwardly, though at asmaller angle of inclination, thus gradually approaching the solid-pole-piece curve B. As the fingers 11 approach saturation, the same action occurs, so that, although the curve reaches practically the same value, at high current, as with the solid pole piece, it has a better voltage regulation for all values of current; that is to say, there is a definite-value of fieldfiux and output voltage for each value of field-exciting current over an exceedingly wide range, as is desirable, for example, in exciter machines.

Also, by substitution of spacing members of magnetizable and non-magnetizable material and of the proper proportions, any desirable shape of curve may. be secured.

.would provide While the precedi description of operating characteristics ie atesto nerators, it is, of course, obvious that a similar-structure good speed regulation when used in a motor.

While I have shown one form of my. invention and described, in detail, one application of the same, it will be obvious to those skilled in the art that it is susceptible of various minor changes and modifications without departing from the s irit thereof, and I desire, therefore, that on y such limitations shall be placed thereupon as are-imposed bv xmm an outer rim portion of magnetic material tobe disposed in the pat of magnetic flux to regulate the density thereof, comprising a plurality of superposed members of magnetizable andnon-magnetizable material, the respective materials of each of said members bein disposed in the same lane and having the oints therebetween isposed in stag.- gere relation with respect to the joints of the prior art or are specifically set forth in the adjacent members.

the a pended claims.

I' c aim as my invention! 1. In a dynamo-electric machine, a field frame, a field-magnet pole piece mounted on said frame, and a spacing member dis osed intermediate said pole piece and said rame and comprising a central portion composed of non-magnetic material and a rim portion composed of magnetic material.

2. In a dynamo-electric machine, a field frame, a field-magnet pole piece mounted on said frame, and a plurality of s acing members disposed intermediate sai pole piece and said frame in stacked relation, said spacing members each comprisin a'central portion composed of non-magnetic material and a rim-portion composed of magnetic material, said spacing members being sq arran ed as to provide magnetic paths of relative y high reluctance at the center of the pole pieces and of successively lower reluctance nearer the sides of the pole pieces.

3. In a dynamo-electric machine, a field frame, a field-magnet pole piece mounted on ly lower reluctance ne said frame and provided with radial slots adjacent the base thereof, and a spacin member disposed intermediate said fiel frame and said field-magnet pole piece and comprising portions of magnetizable and of non-magnetizable material disposed in sideby-side relation, the junction of the magnetic and non-magnetic ortions of the said spacing member being isposed opposite the slots in said ole piece. A

4. A vnamo'electri'c machine frame having a field-magnet 'pole piece, certain base portions of which are cut away, and spacing members composed of magnetizable and non-magnetizable ortions inserted between the frame and sai pole piece. and bridging the spaces formed by cutting away said base portions to provide paths for the magnetic flux of relatively high reluctance at the center of said pole piece and paths of successivearer the sides'of said pole piece. I

-5. A spacing member having an outer portion of magnetic material and a central ortion of non-magnetic material disposed m the same plane.

6. A composite spacing member having 8. A composite spacin member adapted to be disposedin thepat of magnetic flux to regulate the density thereof, comprising a plurality of superposed members of ma frame, a field magnet pole piece mounted on.

said frame, and a spacing member dis osed intermediate said pole piece and said rame and comprising an annular rim portion composed of magnetic material.

10. In a d name-electric machine, a field frame, a fiel -magnet polepiece mounted on said frame, and a plurality of spacing members disposed intermediate said pole piece and said frame in stacked relation, said spacing members each comprising an annular rim portion composed o magnetic material, said spacing members being so arranged as to provide magnetic paths of relatively high reluctance at the center-of the pole pieces and of successivel lower reluctance nearer the sides of the po e pieces.

. 11. In a d amo-electric machine, a field frame, a fiel -magnet ole piece mounted on said frame and provi ed with one or more radial slots adjacent the base thereof and means disposed intermediate said field rame and said field-magnet, pole piece and comprising one or more spacing portions of solid magnetizable material and one or more portions of nonmagnetizable material disposed in side-by-side relation, the junction of the magnetic and non-magnetic portions of the 13. A composite spacin member adapted to regulate the density thereof, comprising to be disposed in the pat of magnetic flux a plurality of superposed annular magnetto regulate the density thereof, comprising izable members of different inner diameters. a plurality of superposed magnetizable spac- In testimony whereof, I have hereunto 5 ing members of diflerent diameters. subscribed my name this 30th day of J an.

. 14. A composite spacing member adapted 1918. to be disposed in the path of magnetic flux DAVID HALL. 

